Packard Forum Index » Pre-War (1899-1942)

Hi All,
Just a query on my temp.gauge.When the motor has warmed up the gauge fluctuates from 160 degrees up to just over the 200 degrees mark. It will stay there for a while then drop back to 180 or down to 160 again. It does this whilst travelling and also when you have a short stop say at traffic lights etc. It does tend to worry me especally when in a traffic jam which we do get a lot of.
I have checked the Radiator when the motor has cooled down and there is always plenty of water right to the top of the Rad.
Is this normal?
Terry

You didn't mention any observations about the operation of the radiator shutters which control the temperature by controlling the airflow thru the radiator core. Erratic shutter performance could cause the situation you describe.

The thermostat is a nominal 160 degree unit because alcohol antifreeze was the dominant material of the era and can boil off at higher temperature. The shutters should begin to open at about 155 to 160 and be fully open by 165 degrees. If the thermostat and shutters are not operating freely and correctly, you'll never have good temperature control.

Typically these cars run at the thermostat rated temperature even on quite warm days when idling and driving at moderate speeds; it's not uncommon for the cars to run a bit warmer at higher speeds due in part to the (numerically) high rear axle ratio which gives high engine rpm. But then returning to 25-45 mph the temperature should again return to or near the thermostat rating.

Yes, if all is operating correctly you'll see a bit of cycling of the temperature as the shutters open fully and begin to retract as the engine temperature drops. But a swing to 200 degrees shouldn't occur except in the most extreme of conditions, like stuck in traffic on a 110 degree day for an hour or more. July is typically a very hot month here, and I've crawled along, stop and go, in parades on July 4th and the temperature may gradually creep to 170 or 180, but within minutes of getting back on the road, the temp drops rapidly back to the normal 160.

If you're in doubt about the thermostat operation, disconnect the thermostat linkage and use a small block of wood or otherwise block the shutters wide open. If you then experience overheating, your problem is more than likely with the engine cooling system, e.g. radiator, water pump, fan belts, collapsing hose, water distribution tube, or related items. I hope you haven't blocked off the water flow to the oil cooler; in order for the coolant to get to the rear of the distribution tube and engine it must pass thru the cooler unless the internal baffles have been altered.

Let us know about the shutter operation and we can go from there.

EDIT - Terry, a couple of other thoughts. Since these cars do not use a conventional thermostat which interrupts the water flow, the temperature in the top radiator tank should be within a few degrees of the gauge reading - get a good laboratory thermometer and check to see that the gauge is accurate. If not, you might consider removing the bulb in the rear of the head to insure that it's not imbedded in crud or otherwise not in the path of the coolant or coated with insulating crud. Also, in cool days it's not uncommon for the car to run at less than the thermostat setting due to very cold air getting past the shutters - on winter days mine often runs as cool as 130 or 140. Does you car exhibit this, or does it always exhibit the overtemp excursions even on cool days?

Terry, I don't know the recent history of your engine but here's a few more things to consider. First, from the day the car leaves the showroom floor the cooling system begins a slow and progressive deterioration. It may take tens of thousands of miles to notice, and maybe you'll never notice it until an engine rebuild because as the rings and cylinder walls wear to a mating pattern, rings gradually loose a bit of tension, and clearances in general begin to open, your engine is creating less heat and thus the cooling system no longer has to be as competent to deal with it. But as soon as engine work like rings, bearings etc. is done, you increase the amount of heat that the cooling system has to cope with and at that point it's gradual deterioration may become noticeable.

Another point - has the radiator been repainted? Some folks like gobs of glossy black paint on their radiator which just acts like an insulator and inhibits good heat transfer. Radiators should be painted only with low-solids paints specifically for that purpose.

Another point to consider - after 70+ years its not uncommon to find very considerable erosion and wear on the water pump impellor so that it no longer is capable of moving the volume of water.

Cheers Dave,
I will try to check out some of these points at the weekend and will update you accordingly.
Terry

Hi Dave,
Discovered the reason for all the backfiring and temperature gauge fluctuations.
It turned out to be the H.T.coils being well past their sell by date and had finally given up the ghost.
Quick phone call to J.D at Max Merritts and he got them in the post for me in time to fit for our local show. The car is now running really sweet with no back firing or drastic fluctuations from the gauge it only reached about 170 degrees on a really hot day. Can't say enough about J.D's service blees him.
Thanks again for all your info
Take care
Terry

H.T. coils? Do you mean the NorthEast ignition coils? The new ones with the cast aluminum base, complete and pretty enough to put on the mantle, are made and sold by Bob Connole, I guess Max is just another middle man. Mine also began acting up some years back and required replacement, the heat just takes it's toll on the insulation and that's why it's just trashing your money to buy NOS coils, also the location on the cylinder head probably doesn't help longevity. The coils inside the new cases are Lycoming aircraft coils I'm told.

I bought mine direct from the maker perhaps 15 years ago, never a problem.

Yes Dave,
They are the ones,and what a difference now.
speak again sometime
Terry